Senior Superintendent Francisco Don Montenegro, Batangas police director, identified the suspect as Aldrin Galicia, 30, a resident of Barangay Pantay here.
Galicias companions, identified as Christopher Pamute, 26, and Michael Rivera, 19, also both city residents, were also held for questioning after unlicensed firearms were found in their possession.
Montenegro said Galicia was identified by an eyewitness from a police file as the gunman in Rosales slay. Police will present Galicia to another eyewitness for further identification.
Galicias group was accosted at a checkpoint for carrying high-powered firearms inside their Toyota Corrola.
Police said murder charges will be filed against Galicia, while his companions will be charged with illegal possession of firearms. Arnell Ozaeta